ichthyosisEnglishOxford Dictionary of Englishichthyosis /ˌɪkθiˈəʊsɪs / ▸ noun [mass noun] Medicine a congenital skin condition which causes the epidermis to become dry and horny like fish scales. – DERIVATIVES ichthyotic /ˌɪkθɪəʊˈɒtɪkɪs/ adjective